Chlorinated anilines are widely used as chemical intermediates in the manufacture of numerous dyes, pesticides, drugs and industrial compounds. The purpose of this study was to examine the nephrotoxic potential of the six dichloroaniline (DCA) isomers in vivo and in vitro. In the in vivo studies, male Fischer 344 rats (4-8 rats/group) were administered a single, intraperitoneal injection of a DCA isomer (0.4, 0.8 or 1.0 mmol/kg) as the hydrochloride salt or given vehicle (0.9% saline, 2.5 ml/kg), and renal function monitored at 24 and 48 h. Renal effects induced by DCA were characterized by decreased urine volume, increased proteinuria, hematuria, modest elevations in blood urea nitrogen (BUN) concentrations, decreased accumulation of p-aminohippurate (PAH) by renal cortical slices, and no change or a slight decrease in kidney weight. Renal morphological changes were observed as proximal tubular necrosis with lesser effects on distal tubular cells and collecting ducts. Based on the overall effects on renal function and morphology, the decreasing order of nephrotoxic potential was found to be 3,5-DCA greater than 2,5-DCA greater than 2,4-, 2,6- and 3,4-DCA greater than 2,3-DCA. The ability for the DCA to induce nephrotoxicity correlated well with the lipophilic properties of the DCA isomers and Hammett constants (sigma) for the various chloro substitutions. In the in vitro studies, renal cortical slices from naive male Fischer 344 rats were co-incubated with a DCA isomer (0-10(-3) M) and PAH or tetraethylammonium (TEA). All DCA isomers decreased PAH and TEA accumulation at 10(-3) M DCA concentration in the media with 3,5-DCA inducing the largest decrease at this concentration. These results indicate that DCA are capable of altering renal function in vivo and in vitro and that 3,5-DCA possesses the greatest nephrotoxic potential in vivo and in vitro.